A/N: I wrote a soulmate AU story. For an AU where whatever marks your roommate's skin (for example, doodles or tattoos) shows up on yours. Wound reappear, too. NOTE: Is a ever tired when I wrote this, so it may be a little strange at times. And I couldn't get to editing, but I'll re-do that tomorrow.
Disclaimer: Nothing belongs to me, all right go to Bryke and Nickelodeon

Growing up, Katara never truly has anybody her age to talk about her soulmarks with. Sokka is out of the question, and there are no girls her age in the village. So she talks to her mother. There are days where she wakes up to find her skin covered in burn scars and bruises, and sometimes she awakens with blood streaming from a cut on her arm or finger.
She is sure her soulmate must have a rough life.
So she asks her mother for advice. Her mother wraps her arms around her daughter lovingly, and tucks a stray curl behind her ear before telling Katara to contact her soulmate, in common script, which Kya promises to teach her. Sokka enters just after the and timidly asks if she could teach him too, to which she laughs and ruffles his hair as she tells him she will.

And so, painstakingly, tediously, she teaches her children enough common script so that they can reach their soulmates.
Katara's first message is simple. It reads, in carefully spelt out characters on her right wrist:
'Hey, I'm Katara. I'm from the Water Tribes.'
She doesn't specify which because her father told her not to.
'And from where are you?'

The next day, she finds neat characters tucked under hers.
'Hi. My name is Zuko. I'm from the Fire Nation, and I'm a firebender. Are you a waterbender?'

She shows the message to her father, because she can't read all of it, but knows that there is something about the Fire Nation, which she does not understand. Upon seeing the message, her father frowns.

"Judging from the character and language style, that boy seems to be from the Fire Nation upper classes. Probably the son of some successful general." His voice hardens. "Do not tell him under any circumstances that you are a Southern waterbender. You can only tell him that you're from the South, noy that you are a waterbender."

So Katara tells him she's from the South. She does not comprehened her father's reasons, but she follows his wishes like the good girl she is.

-oOo-

A few years later, when she is eight, the black snow falls and her mother is mercilessly slaughtered, almost right in front of her own eyes.
Sobbing and hopeless, she writes to Zuko. She has learned a lot about him in the past years, and the reason for their connection and either been forgotten by both or is being avoided by them.
She has learned that he likes the story of the Blue Spirit and has been training swordfighting and firebending from a rather young age. She also knows he has a little sister and a mother who he holds very dear to himself. She hopes he will be able to help her, maybe his mother can be a second mother to her via their connection.
He tells her stories about his mother and his cousin, who seems to be in the war with his uncle, and he misses very much.
It is not quite what she wanted, but she is content enough with it.

-oOo-

It is not too long until he needs her himself. His mother mysteriously vanished from home last night and he is panicking and doesn't know what to do or say. Katara, in-turn, tells him stories of Sokka and her father's antics, and some of Bato's misadventures.
From that day onwards, she can tell the amount and harshness of his scars only increases.

-oOo-

It happens when she is eleven. She wakes up in the middle of the night to a searing pain over her left eye. Scared, the young girl calls for her grandmother. The wizened woman come into her grand-dsughter's room and almost drops her oil lamp when she sees her.
The waterbender, of course, is confused about Kanna's reaction, but when the old woman wordlessly shows her her reflection, she shrieks, and presses her face against the icy walls of the iglu. Somethign is not right with the boy on the other side of the bond. Frantically, she searches her body for signs of other burns or even a witness report. On her left lower arm, she suddenly finds a message, but it's not in Zuko's neat yet sprawling characters.

'Hello young lady. At least, I presume you are a young lady. This is Iroh, Zuko's uncle. My nephew got into a bad incedent involving bending, and recieved the scar in the process. I hope you can cover it up well with make-up or heal it, it would be most fortunate for Zuko. Good news is: We might be paying visit to the South soon!
- Iroh'

The girl does as commended and learns to put on make-up so that the scar became less evident. Zuko tells her he doesn't mind it or need it covered that often, and that he likes his scar as it made him feel tougher.

-oOo-

One day, she finds a meaningful message on her wrist.

'Dear Katara,
I'm probably going to show up at the South Pole in the next few weeks, so it's time I tell you the full truth.
My name is Crown Prince Zuko of the Fire Nation.
My father is the Fire Lord and burned me for speaking out of turn for the behalf of rookie soldiers. Three years ago. Ever since the, I've been searching for the avatar. It's the only way I can come home and restore my honour.
My uncle, who sent you that kind note when I was first scarred, is the Dragon of the West.
I'm sorry for not telling you sooner. I hope my people do less harm in the future. Please, at some point, forgive me.
- Zuko'

She she recieves that letter, her heart almost stops. She suddenly becomes aware of what that message means.

The disgraced crown prince of the Fire Nation is her soulmate.